To analyze the process involved in maintaining conversational coherency, the study described in this paper used a construct called a "context space" that grouped utterances referring to a single issue or episode. The paper defines the types of context spaces, parses individual conversations to identify the underlying model or structure, and identifies the following elements of coherent conversations: topic discernment; semantic, structural, and state rules that maintain coherence; focus levels; and linguistic mechanisms such as clue word shifts, explicitly labelled shifts, modes of reference, repetition of words, and tense shifts. Based on these conversation elements, a process model is outlined that requires a conversant to respond appropriately to preceding utterances, and to integrate a speaker's utterance with preceding utterances. Appendixes include state assignment rules for a context space, semantic relational rules determined by the underlying structure of a conversation, and a focus level algorithm for the constituents of a given context space (the actors, objects, events, issues, location, time, and duration period). (MAI)